Torque wrench



April 1l, 1950 F. W, LNERMONT v v Y 2,503,499

TORQUE WRENCH 'Filed March 20, 1945 Patented Apr. 11, 1950 rroRQUE WRENCH Frank W. Livermont, Los Angeles, Calif., assignor to Richmont, Inc., Los Angeles, Calif., a corporation of California Application March 20, 1945, Serial No. 583,698

4 Claims. 1

This invention relates to torque wrenches, and more particularly to a wrench adapted for the settingup of a threaded member at a predetermined torque. Tools oi the above charac-ter are now widely employed for the purpose of making up threaded connections under deiinite torque requirements, but considerable diiiiculty has been encountered in the development of a tool which will operate over extended periods of time under the same torque conditions due in many cases to the development of friction within the structure itself as differentiated from the frictional characteristics of the tool used for determining the yielding characteristics of .the clutch means through which the said torque requirements are established.

It is therefore an object of this invention to provide a torque wrench in which means are provided or determining the torque characteristics of the clutch means incorporated therein and wherein means are provided which are operable to maintain the constancy of the torque requirements in an order to cause the clutch means to release upon reaching the setting thereof required to permit the clutch means to yield under increased torque.

Another object of this invention is to provide a yielding clutch element in a torque wrench which includes a tool supporting shank carried within a tool holder, a torque clutch mounted within the holder adapted to be releasably engaged with the tool holder, and yieldably associated with a torque determining means mounted within the tool holder so as to permit'I the holder to be rotated with relation to the tool supporting shank upon development of the torque existing between the holder and the shank in excess of that determined by the torque determining means.

`Other objects and advantages of this invention it is believed will be apparent from the following detailed description of a preferred embodiment thereof as illustrated in the accompanying drawings.

In the drawings:

Figure 1 is an elevation principally in vertical mid-sectlon of a torque wrench embodying my invention.

Figure 2 is a sectional view taken substantially on the line 2-2 of Figure 1.

In the preferred embodiment of my invention as the same is illustrated in the accompanying drawing, I indicates a handle which, as illustrated, includes a hollow tool supporting branch 2 2 and a hollow crosshead 3. The hollow cross'- head 3 forms the gripping section of the handle. Mounted within the branch 2 is a tool shank v4 which projects from the branch 2 and is pro' vided with a head 5 of common form which may.'

be releasably secured to a suitable size wrench head E for coupling with the threaded member which is to be threaded to a companion which isi with the interior diameter of the branch 2.'

Means may be provided for permitting the tool shank 4 to ratchet in one direction on rotation of the handle 3 in one direction, which means as herein illustrated are:

The bearing section 'I is divided intermediate its length toprovide a second bearing section Ia which likewise ts closely within the interior diameter of the bran-ch 2. Between the sections 'I` and 'IR `there are provided ratchet teeth 8 which provide gripping surfaces on rotation of the handle in one direction but which are inclined so as to permit the teeth of thesection 'Ia to ride over the corresponding teeth of the section 'I upon reverse rotation of the handle I. In orderto maintain theteeth 8 of the two sections 'l and la.

yieldably-in engagement, a spring 9 is mounted around the reduced section III of the shank 4 and engages the;end shoulder II of the bearing section l at one end and a plug I2 threaded to the end of the branch 2 at its opposite end.

Means are provided for determining the torque which may be exerted between the handle I and the shank 4 for rotating the shank 4 upon rotation of the handle I, which means, as herein illustrated comprise a cam head I4 formed at the upper end of the shank 4 and provided with a multiplicity of cam faces I5. Mounted within the bore of the transverse crosshead 3 of the handle I is a cam block I6, the end I6EL of which is adapted to be engaged with any one of the faces of the cam head I4.

A spring II is mounted Within the transverse crosshead 3 of the handle I to urge the cam block I6 against the faces of the cam head I4. A plug I8 is threaded into the transverse branch to engage the end of the spring l1 and to determine the degree of compression of the spring I1 and hence the force with which the spring Il urges the block I6 against the cam head I4:

It is usual in such tools to seal this adjustment after the tool has been set up under the required torque conditions. Thus the plug I8 is threaded into the interior of the crosshead 3 suiiiciently to permit a seal to be mounted at the end of the crosshead 3 beyond the plug I8, such a seal being diagrammatically indicated at I9.

In order tov determine the frictional resistance of the shank 4, to rotation within the branch 2 so that the friction developed will be necessarily constant, I have provided means within the crosshead 3 for resisting the transverse thrust imposed against the head I4 by the force of the spring I'I acting through the block I6. I have found that utilizing the particular type of clutch illustrated that the force exerted by the spring I'I may be, and is under most instances, sufficient to cause great variation in the resistance of the shank 4 to rotation within the branch 2 due to the bending force which is imposed against the head I4 tending to bend the shank 4 in the branch 2. In order, therefore, to maintain the frictional characteristics ofthe tool constant, I provide a yoke member 2D which is slidably mounted in the crosshead 3 in position directly opposed to the direction of operation of the spring I 'I acting against the cam block I 6. The yoke member 20 is slidably mounted within the crosshead` 3 and its position with relation to the shank 4 is determined by a plug 2| which is threaded withinv the crosshead at the end opposite the plug I8. The yoke member 20 is formed at its end with a reduced section 22 providing a semicylindrical yoke element 23, the diameter of which corresponds substantially with the diameter of the reduced section 24 of the shank 4. The reduced cylindrical section of the shank 4 lies immediately above the center line oiv the cam head I4 so that the point of application of pressure or of resistance to the pressure exerted by the block I 6 against the head I4 is below the center line of the block I6 and takes up any tendency o the shank 4 to be bent transverse of its axis due to the pressure exerted thereagainst by the spring I'I. As the semi-cylindrical yoke 23 is in metal to metal contact with the ,cylindrical section 24 of the shank 4, a denitefrictional characteristic is developed against the rotation of the shank 4 Within the handle. This frictional characteristic is determined by the adjustment of the plug I 8 in the crosshead 3 which holds the block I6. against the. face I of the cam head I4' and, being once determined with relation to the force exerted by the spring I'I, remains substantially constant. In actual practice the plug 2| is threaded into the crosshead 3 to join the shank 4 against the inner surface of the branch 2, and the plug 2| is then backed off to relieve the shank and position the same centrally of the branch 2. The sections 1 and 'Ie are turned to give a clearance of approximately .030 inch. Within the bore of the branch 2. Thus the principal frictional resisting rotation of the shank 4 is between thel yoke 23 and the block I6.

I have found that on utilization of a tool of the above character without a denite resistance to the bending force exerted against the head I4, that the torque determined by the spring I'I as measured in inch pounds at the tool connection 5 will vary over several inch pounds as the shank 4 rotates to bring different faces I5 of the cam head I4 into engagement with the cam block I6V substantially without regard to the accuracy with which the said faces are milled upon the head, I4. It only requires apparently a very slight degree of inaccuracy of machining of the tool throughout its parts to cause a, Very great differential between the inch pounds of torque required to rotate the shank 4 Within the handle against pressure of the spring II unless the head I4 is supported so that it is impossible for the same to have a bending force transmitted thereto which in turn is operable to vary the amount of friction which will be exerted between the bearing sections 'I and Ia of the shank 4 within the branch 2. Where a tool is required which will give an accurate determination of the torque exerted against the threaded connection, the variations are sufficient to destroy the utility of such a torque tool unless means as I have herein illustrated are provided for maintaining constancy of friction conditions within the structure of the tool.

It will be observed from Figure 1 that the cam head I4 is divided by the cylinder portion 24 to divide the bearing faces I5 that engage the block I6 into two portions of unequal -width distributed above and below the longitudinal center of the cylindrical cam block I6. The effect of this is to rotate the block IS each time the spring I'I is depressed by the force exerted to rotate the handle l, overcoming the torque resistance to rotation of the shank 4 within the handle. An important result is accomplished by such rotation of the block I6 which result is the changing of the area of the block end I6El that is engaged with the face I5 of the cam head, avoiding uneven wear of the end of the block I6.

Having fully described my invention, it is to be understood that I do not Wish to be limited to the details herein set forth, but my invention is of the full scope of the appended claims.

I claim:

1. In a torque yielding tool, the combination of a handle member having a shank positioning branch and a crosshead, a tool shank rotatably mounted within the handle, the tool shank having a cam head extending into the crosshead and a 'bearing portion interposed therein, a cam block mounted Within the crosshead engaging the cam head, a spring member yieldably urging the cam block against the cam head, a yoke block mounted in the crosshead in the portion thereof opposed to the spring, positive means threaded in the crosshead for determining the position of the yoke within the crosshead, and the yoke having a semi-cylindrical portion engaging said bearing portion of said cam head to resist a bending moment. of the shank imposed thereagainst by the spring acting against the crosshead.

2. In a torque yielding tool, the combination of a handlev member having a t-ool shank receiving branch and a crosshead, a tool shank rotatably mounted within the said branch, the tool. shank having a cam head providing a multiplicity of cam faces and a bearing face, a cam block mounted in the crosshead in position to engage the said cam faces, a spring mounted within the crosshead. to urge the block against the cam faces of the cam head, means threaded in the crosshead for determining the pressure exerted by the spring against the cam block, a yoke block positioned in the crosshead at the side thereof opposite from said cam block and including a yoke section adapted to engage said bearing face, and means for positively positioning said yoke to resist the bending moment imposed against the tool shank by the pressure of the spring.

3. In a torque yielding tool, the combination o1' afhandle/member, a tool shank rotatably mounted within the handle member, the tool shank having a cam head, a cam block engaging the head in a direction transverse to the axis of the tool shank, a spring yieldably urging the block toward the cam head, means positioned Within the handle member acting in opposition to the force exerted 'against the cam block by the spring to maintain the shank leoncentrically positioned Within the handle member and the cam head being positioned with relation to the longitudinal axis of the cam block so that there is an unequal bearing between the cam head and the cam lblock upon portions of the block on opposite sides of the longitudinal center whereby the cam block will be rotated when the shank rotates Within the handle.

4. A limited torque tube comprising: a T- shaped body dening a tool sleeve and a cross bore; a rotatable tool shank in said sleeve projecting into said cross bore and provided with at least one cam face and with a journal portion; opposed plungers slidable in said cross bore, one of said plungers engaging said journal portion and the other of said plungers engaging said cam face; a spring and adjustment means for said cam face engaging plunger to apply a pre-selected force tending to resist rotation of said tool shank portion; and other positive adjustment means for said journal engaging plunger adapted to oppose the force of said spring to resist any bending moment on said shank exerted by said spring.

FRANK W. LIVERMONT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

